US businesses cranked up hiring in January in a burst of job growth that pulled the US unemployment rate down to 8.3 percent, nearly a three-year low, official data showed Friday. But Matt McDonald at Hamilton Place Strategies said the decline in the labor force participation rate, to 63.7 percent from 64 percent in December, was a worrying sign that people are still dropping out of the workforce. "If that full participation rate is the goal, our economy is 'missing' 3.8 million workers," McDonald said. The blockbuster jobs report blew past expectations, providing a shot of good news for President...